Hand grenade

ABSTRACT

The invention relates to an airburst hand grenade. Existing constructions of fragmentation grenades all have one basic shortcoming; the active fragments are very unlikely to find the target owing to the fact that detonation takes place with the hand grenade lying on the ground, whereby the effect does not occur. The invention solves the above problem by a hand grenade being caused to jump 1-2 m above the ground before detonating. This means that the fragments will be spread essentially horizontally and at an angle (v) to the ground and consequently attack the target from above, which results in a many times larger target surface and the capability of spreading fragments behind a shelter.  
     The hand grenade comprises a mechanism ( 1 ), a detonator ( 2 ), a warhead ( 14 ) and support legs ( 9 ) for raising the hand grenade from a horizontal position to an upright position. The detonator ( 2 ) comprises a delay unit ( 3 ), an upper charge ( 4 ) which can release the support legs ( 9 ) by removing a locking cover ( 8 ), a jump charge ( 5 ) which can throw the warhead ( 14 ) above the ground, and an explosive cartridge ( 6 ) which can initiate a main charge ( 13 ).

The invention relates to a hand grenade with an airburst.

Existing constructions of fragmentation hand grenades all have one basicshortcoming; the active fragments are very unlikely to find the targetowing to the fact that detonation takes place with the hand grenadelying on the ground, whereby the effect does not occur.

Fragmentation hand grenades have a casing which strives to spreadfragments uniformly in all directions, see for instance U.S. Pat. No.4,781,117 A. This means that the major part of the fragments is directedinto the ground or into the air when detonating. Only the few fragmentsthat start from a horizontal ring round a lying hand grenade constitutea potential danger to a lying target. An irregularity or depression inthe ground which is as high as the height of a lying hand grenadeconstitutes a direct obstacle to a hit. A minimum irregularity in theground affords the target natural protection also at a distance of lessthan 1 m. It is also highly probable that such obstacles exist in eachthrow.

A solution to this problem is demonstrated in U.S. Pat. No. 5,866,841 Awhere a hand grenade has a plurality of legs which are unfolded andraise the hand grenade to a vertical position after it has come to reston the ground. This means that no fragments will be directed into theground where their effect is wasted. However, there remains the problemwith irregularities that still constitute an obstacle to a hit. Besides,in combat using hand grenades a target will only by mistake be locatedin a position other than lying and thus is not exposed to the fragments.This means that the excellent penetration values of a modern handgrenade do not matter since the fragments will not reach the target.

The invention solves the above problem by a hand grenade being caused tojump 1-2 m above the ground before detonating. Thus the fragments willattack the target from above, which results in a target surface that ismany times larger and makes it possible to give off fragments behind ashelter.

The invention will now be described in more detail with reference to thefollowing Figures:

FIG. 1 shows the use of a hand grenade according to the invention, and

FIG. 2 is an exploded view of a hand grenade according to the invention.

A hand grenade according to the invention is handled largely as anordinary hand grenade. Once the hand grenade is thrown, a pyrotechnicdelay unit (3) starts in the hand grenade detonator (2). As the handgrenade lands in the target area and is lying still on the ground, thedelay unit (3) releases a pyrotechnic charge (4) in the upper part ofthe hand grenade detonator which shoots away a locking cover (8) fromthe upper side of the hand grenade. When the locking cover (8) has beenremoved, a number of, for instance 5-6, support legs/spring legs (9) arereleased, which are articulated to a spring leg mounting (10) in thebottom of the hand grenade. The support legs (9) unfold at 90 degrees inall directions and raise the hand grenade from a lying horizontalposition to a standing vertical position, with the mechanism (1) facingupwards and the spring leg mounting (10) in the bottom surrounded by thesupport legs (9) which form a star-shaped support against the ground. Aguide tube (7) is fastened centrally in the spring leg mounting (10) bya thread and moves loosely in a tubular duct (19) through the grenadebody. The guide tube (7) extends through the entire grenade body andterminates in contact with the hand grenade detonator (2) in the upperpart of the grenade. The delay unit (3) initiates a pyrotechnic jumpcharge (5) in the bottom of the hand grenade detonator. The gas pressurefrom the charge (5) acts on the guide tube end surface (18). The guidetube (7) which is in contact with the ground by the intermediary of abase plate (16) will be pressed against the ground whereas the handgrenade will be pressed upwards. When the hand grenade has reached aheight of 1-2 m, the delay unit (3) releases an explosive cartridge (6)in the lowermost part of the detonator. The explosive cartridge (6)ignites the main charge (13) of the hand grenade which detonates. If anairburst is not desired, the guide tube (9) can be unscrewed from thespring leg mounting (10) in one motion and removed from the handgrenade, thereby preventing jumping. The detonation then occurs lying onthe ground.

FIG. 2 is an exploded view of a preferred embodiment of a hand grenadeaccording to the invention. The hand grenade has a mechanism (1) whichcan be a prior-art standard mechanism with striking pin, mainspring,handle and safety catch. The lower part of the mechanism housing isprovided with a fixedly joined circular sheet (15) whose diameter isslightly larger than the mechanism housing. The sheet (15) serves as aseal against and holder of the locking cover (8) on the upper side ofthe hand grenade. The mechanism (1) has an internal thread for the handgrenade detonator (2).

The locking cover (8), is a cylindrical cover, which fits tightly overthe upper part of the grenade body. Its edges (17) extend somewhat downalong the sides of the grenade body and lock the spring legs (9) againstthe sides of the grenade body.

Centrally there is circular hole whose diameter is slightly smaller thanthe sheet (15) of the mechanism housing, which sheet can thus hold thelocking cover (8) in place, squeezed between the mechanism sheet (15)and the grenade body. Here are also moisture-proof seals arranged. Whenthe upper pyrotechnic charge (4) of the hand grenade detonator isinitiated, a gas pressure is generated, which acts against the undersideof the locking cover with such a force that the locking cover (8) isdeformed and urged past the mechanism (1). When the locking cover (8)has been removed, the spring legs (9) are released.

The hand grenade detonator (2) consists of a continuous tube with acylindrical waist with an increased diameter. In the upper part of thetube there is a detonating composition (11) which is initiated by thestriking pin of the mechanism. From the detonating composition (11)extends, axially through the tube, a duct containing a delay unit (3)which in the lower part may pass into another unit of a pressed typewith improved time performance. The delay unit is in this example apyrotechnic unit but may just as well be electric. An explosivecartridge (6) is arranged in the lower part of the tube. The waistsurrounding the tube has an upper and a lower space which are separatedfrom each other by intermediate material. The circumferential surface ofthe waist is provided with a thread connecting to the upper part of thegrenade body. The upper space will thus be located on the outside of thegrenade body and the lower space in the interior of the grenade bodyimmediately above the inserted guide tube (7). Both spaces are axialrecesses in the material of the waist, which annularly surround thetube. The spaces communicate with the delay unit (3) of the tube throughone or more radial apertures (20). The spaces are filled with apyrotechnic unit (4, 5) whose function in the upper case is to removethe locking cover (8) and, in the lower, to generate gas pressure tocause jumping upwards. The charges (4, 5) are environmentally protectedby varnish, lids or the like. The upper part of the tube is providedwith a thread to which the hand grenade mechanism (1) connects. Between2 and 2.5 s after the delay unit (3) of the tube has been initiated, thefirst pyrotechnic charge (4) will fire away the locking cover (8), theremoval of which releases the spring legs (9) which in turn raise thehand grenade to an upright position. After further 0.5 to 1 s, the innercharge (5), the jump charge, is initiated and throws the hand grenadeupwards between 1 and 2 m. Finally, when an optimal height has beenreached, the delay charge (3) triggers the explosive cartridge (6) andthe hand grenade bursts. The times mentioned above are approximationsand calibrates to achieve an optimal effect.

The guide tube (7) moves freely but in a moisture-proof manner in a duct(19) in the core line of the grenade body. Its upper end connects to thehand grenade detonator (2) and the jump charge (5) thereof. There italso encloses the explosive cartridge (6) which in its entirety extendsinto the tube (7). The guide tube (7) thus constitutes an interruptionin the ignition chain, I.e. before a jump has occurred or the guide tube(7) has been removed, initiation of the main charge (13) cannot takeplace. This is an important improvement of safety compared withprior-art constructions where the explosive cartridge is storedseparately and fastened in the hand grenade when required. The lowerpart of the guide tube is fastened in the centre of the spring legmounting (10) by a continuous thread.

The guide tube (7) is held vertically upright by the unfolded springlegs (9) and thus also the hand grenade body. When the jump charge (5)is initiated, the gas pressure will act on the end surface (18) of thetube and a force will arise between the guide tube (7) and the grenadebody. The relatively great length of the guide tube will guide thegrenade body to maintain its orientation also during the jump phase.Here also a minor rotation may be introduced if required for stability,for instance by grooving. A fixedly connected base plate (16) isarranged under the thread of the guide tube. Thus the base plate (16) ispositioned under the spring leg mounting (16) and constitutes the lowerboundary of the hand grenade and its contact surface on the ground. Thebase plate (16) is given a suitable design to increase friction againstthe ground if rotation is necessary. The base plate (16) has a somewhatlarger diameter than the spring leg mounting (10) with the spring legs(9) folded back and its edge is grooved so as to provide a good grip forthe thrower's fingers. The thrower can thus easily unscrew and removethe guide tube (7) and thus also the base plate (16) immediately priorto throwing if a ground detonation is desired. Alternatively the guidetube (7) and the base plate (16) with thread can be separate parts whichonly move in each other. Then the jump function would not occur if thebase plate (16) was removed and thus the mounting of the guide tube wasremoved. The guide tube (7) would remain in the grenade body andconsequently still constitute an interruption in the ignition chainuntil the guide tube (7) is fired away by the pyrotechnic charge (5).

In the preferred embodiment, six support legs/spring legs (9) areuniformly distributed round the grenade body. They are locked in theupper part of the edge (17) of the locking cover and are articulated tothe spring leg mounting (10) where also the spring function is to befound. Under the edge (17) of the locking cover, the upper part of thespring legs (9) hooks into a shoulder or a notch in the grenade bodywhich locks the spring legs, and thus also the spring leg mounting tothe grenade body in a fixed position. The locking ceases by the lockingcover (8) being removed. Then the spring legs (9) unfold at 90 degreesfrom the core line of the grenade body and raise the lying hand grenade.The spring legs (9) are either separate components which jointly coverthe circumferential surface of the entire grenade body and are thereforeformed to good gripping surfaces for the thrower's hand, or somewhatlowered into grooves in the circumferential surface and may then consistof merely the springs themselves.

The spring leg mounting (10) is a sheet which is separate from thegrenade body and which in its periphery constitutes the point ofarticulation for the spring legs (9) and the abutment for theprestressed springs. The abutment for the springs may also consist ofthe guide tube base plate (16) which directly engages the underside ofthe mounting. Consequently the base plate (16) of the guide tube willobtain automatic friction locking while at the same time the springforce in the raising function does not occur when a ground detonation isselected, which may be desirable. The guide tube (7) is positioned inthe centre of the spring leg mounting (10) in a threaded through hole.

The warhead (14) of the grenade body consists of a shell of preformedfragments (12) cast into a plastic matrix. In the grenade body, asuitable explosive is cast to a main charge (13). Centrally in the coreline of the grenade body there is a continuous plastic lined duct (19).The threaded joint for the hand grenade detonator (2) is arranged at theupper end of the duct. There are also surface ducts arranged fordistribution of the gas pressure from the upper pyrotechnic charge (4)to the inner surface of the locking cover. At the lower end there is amoisture-proof seal against the guide tube (7) which runs in the duct.The guide tube (7) guides the grenade so that the mechanism (1) isoriented upwards at the moment of detonation. Thus the entire undersideand also the sides of the grenade may be given such a softly roundedconical shape that the major part of the total number of fragments ofthe hand grenade are directed downwards to the circle on the groundwhere the effect is to be expected. A minor part of the fragments fromthe top surface of the grenade body are allowed to be spread upwards sothat a certain degree of coverage in that direction is obtained if aground detonation has been selected. The shape and material of thefragments are selected so that an effect on predetermined targets isobtained within the desired effective radius and then ceases as soon aspossible in order to minimise the risks to the thrower. Preforming ofthe fragments provides this possibility of guiding. The explosive in themain charge (13), and optionally a primary charge, and also the point ofinitiation are selected to achieve the above. The conical shape of thegrenade body results in sufficient space for the spring leg mechanism inthe bottom of the grenade. The spring legs (9) will also guide thecontact surface of the hand grenade with the thrower's hand so that hedoes not have to handle a cone but a well-shaped surface.

The locking cover charge and the jump charge of the hand grenadedetonator need not be symmetrical as in the drawing. The locking covercharge (4) can be shallower and have an increased diameter. The jumpcharge (5) should be narrower, as close as possible to the diameter ofthe guide tube (7). The spring legs (9) may consist of the springsthemselves, without separate leg parts, which extend in grooves in theplastic casing of the hand grenade which is then adjusted for a goodgrip. The guide tube (7) can be made in two parts, tube and base plate(16) with thread. A cylinder having the inner diameter of the tubeprotrudes from the thread into the open lower part of the tube. The tubeis kept in place in the duct (19) by an O-ring when the base plate (16)has been removed.

Airburst solves the problem with poor target access. If the hand grenadeis made to detonate at a height of between 1 and 2 m, about half of thefragments will hit the ground within the circle where the speed of thefragments is still such that an effect may arise. Targets located withinthe circle will, independently of posture, expose a considerably largersurface to fragments and thus receive a many times greater amount offragments. The angle (v) of the fragments will be from above orobliquely from above, which fully eliminates small topographicalformations as shelter. Also destroyed walls, furniture, large logs,stones and pits in the ground will be wholly or partly eliminated asshelter depending on the angle (v) of the fragments. The obstructingeffect of snow disappears even if the hand grenade can jump out of thesnow.

According to the invention, the path of the hand grenade is controlledin the jump and, thus, without tumbling. As a result, the warhead (14)can be designed so that the fragments (12) are collected and directedtowards the area where the greatest effect can be achieved, instead ofbeing spread spherically in all directions, which increases theprobability of hitting the target If a traditional ground detonation isdesired, a change is made by unscrewing the guide tube (7) from the handgrenade in one motion. A hand grenade according to the invention gives aconsiderable improvement over prior art which spreads fragments in alldirections and in which the major part of the fragments will be lost.

1. A hand grenade comprising a mechanism (1), a detonator (2), a warhead(14) and a device for raising the hand grenade from a horizontalposition to an upright position, characterised in that the hand grenadealso comprises means throwing the warhead (14) into the air before itbursts.
 2. A hand grenade as claimed in claim 1, characterised in thatthe warhead (14) comprises a main charge (13) and fragments (12).
 3. Ahand grenade as claimed in claim 2, characterised in that the warhead(14) when bursting spreads the fragments (12) essentially horizontallyand at an angle (v) towards the ground.
 4. A hand grenade as claimed inclaim 2, characterised in that the detonator (2) is thrown into the airwith the warhead (14) to initiate the main charge (13).
 5. A handgrenade as claimed in claim 1, characterised in that the device forraising the hand grenade from the horizontal position to the uprightposition comprises one or more support legs (9) arranged round the handgrenade.
 6. A hand grenade as claimed in claim 5, characterised in thatthe support legs (9) are arranged in a spring leg mounting (10) in thebottom of the hand grenade, and that the support legs (9) are raised toan upright position along the grenade body and fixed to the top of thehand grenade by means of a locking cover (8).
 7. A hand grenade asclaimed in claim 6, characterised in that the detonator (2) comprises apyrotechnic charge (4) for pressing the locking cover (8) upwards andreleasing the support legs (9).
 8. A hand grenade as claimed in claim 1,characterised in that the means for throwing the warhead (14) into theair comprises a pyrotechnic charge (5).
 9. A hand grenade as claimed inclaim 1, characterised in that the means for throwing the warhead (14)into the air comprises a guide tube (7), which is movingly arranged in aduct (19) in the warhead (14).
 10. A hand grenade as claimed in claim 9,characterised in that the guide tube (9) guides the jumping up of thewarhead (14) so that the direction is maintained.
 11. A hand grenade asclaimed in claim 9, characterised in that the guide tube (9) guides thejumping up by rotating the warhead (14).
 12. A hand grenade as claimedin claim 2, characterised in that the hand grenade comprises a safetydevice which is capable of preventing the detonator (2) from initiatingthe main charge (13).
 13. A hand grenade as claimed in claim 12,characterised in that the safety device comprises a guide tube (7)arranged between the explosive cartridge (6) and the main charge (13).14. A hand grenade as claimed in claim 1, characterised in that the handgrenade comprises a base plate (16) with sufficient friction against theground to allow controlled throwing into the air of the warhead (14).15. A hand grenade as claimed in claim 2, characterised in that thedetonator (2) comprises a delay device, an upper charge (4) which iscapable of releasing a support leg (9) by removing a locking cover (8),a jump charge (5) which is capable of throwing the warhead (14) abovethe ground, and an explosive cartridge (6) which is capable ofinitiating the main charge (13).
 16. A hand grenade as claimed in claim15, characterised in that the delay device is a pyrotechnic delay unit(3) or an electrical delay device.
 17. A hand grenade as claimed inclaim 15, characterised in that the warhead (14) comprises an axial duct(19) in which a guide tube (7) is slidably arranged.
 18. A hand grenadeas claimed in claim 15, characterised in that the device for raising thehand grenade comprises two or more support legs (9) articulated to aspring leg mounting (10).
 19. A hand grenade as claimed in claim 18,characterised in that the support legs (9) are resiliently raised to anupright position along the warhead (14) and, in the raised position,fixed by means of a locking cover (8).
 20. A hand grenade as claimed inclaim 19, characterised in that the guide (24) and the base plate (16)are releasably arranged on the spring leg mounting (10).
 21. A handgrenade as claimed in claim 9, characterised in that the guide tube (7)comprises an upper end surface (18) on which the combustion gases of thejump charge act to throw the warhead (14) into the air.
 22. A handgrenade as claimed in claim 1, characterised in that the hand grenadecan be made to burst resting on the ground by manually removing a guidetube (9) and/or a base plate (16